To satisfy an increasing need for wireless data traffic, communication systems have been developed to support higher data rates. A communication system may improve spectral efficiency and increase channel capacity to address the increasing need, for example, by various communication schemes such as an Orthogonal Frequency Division Multiplexing (OFDM) scheme, a Multiple Input Multiple Output (MIMO) scheme, and the like.
However, it is difficult to satisfy a need for increasing data traffic in a communication system using the noted schemes for improving the spectral efficiency and increasing the channel capacity. Specially, an increase in use of a smart phone, a tablet, and the like and an increase of applications which use data traffic accelerate a need for increased data traffic.
In a communication system, there is a need for a Radio Frequency (RF) technology which may cover a relatively wide dynamic range and a RF element control scheme using an Automatic Gain Controller (AGC).
A structure of a related art communication system will be described with reference to FIG. 1.
FIG. 1 schematically illustrates a structure of a communication system according to the related art.
Referring to FIG. 1, the communication system includes a signal transmission apparatus and at least one signal reception apparatus. In FIG. 1, it will be assumed that a base station 100 is the signal transmission apparatus, a terminal 150 is the signal reception apparatus, and the communication system includes one base station and one terminal.
A relationship between the base station 100 and the terminal 150 may be expressed using various values, including PTX, L, G1TX, and the like. The value PTX denotes transmit power of the base station 100, and may be referred to as the transmit power PTX, the value L denotes path loss, and may be referred to as the path loss L, and the value G1TX denotes an antenna gain of the base station 100, and may be referred to as the antenna gain G1TX. The path loss L may be determined according to a distance D between the base station 100 and the terminal 150.
If a minimum path loss LMIN is considered, as path loss which occurs in a case that the distance D is a minimum distance DMIN, a maximum receive power PRX—MAX 101 of the terminal 100 is calculated as expressed in Equation (1).
If a maximum path loss LMax is considered, as path loss which occurs in a case that the distance D is a maximum distance DMax, minimum receive power PRX—MIN 103 of the terminal 100 is calculated as expressed in Equation (2).PRX—MAX=PTX+G1TX—MAX−LMIN  Equation (1)PRX—MIN=PTX+G1TX—MIN−LMAX  Equation (2)
In Equation (1), G1TX—MAX 105 denotes a maximum antenna gain used in the base station 100. In Equation (2), G1TX—MIN 110 denotes a minimum antenna gain used in the base station 100.
A dynamic range DR1 of an RF end included in the signal reception apparatus, such as the terminal 150, may be determined using a difference between the maximum receive power PRX—MAX 103 and the minimum receive power PRX—MIN 101. The dynamic range DR1 of the RF end included in the terminal 150 is calculated as Equation (3).DR1 [dB]=PRX—MAX−PRX—MIN  Equation (3)
A gain value which is used in a Low Noise Amplifier (LNA), included in a reception circuit in the terminal 150, and a gain value which is used in a Variable Gain Amplifier (VGA), included in the reception circuit in the terminal 150, should be determined by considering the dynamic range DR1 calculated in Equation (3).
The gain value of the LNA and the gain value of the VGA are determined through a control operation of the AGC, and control operations of the AGC are based on average power measured for a signal outputted from a MOdulator/DEModulator (MODEM).
A structure of a related-art communication system has been described with reference to FIG. 1, and an inner structure of a terminal in a conventional communication system will be described with reference to FIG. 2.
FIG. 2 schematically illustrates an inner structure of a terminal in a communication system according to the related art.
Referring to FIG. 2, a terminal includes an LNA 201, a mixer 203, a VGA 205, an Analog to Digital converter (A/D) 207, a MODEM 209, and an AGC 211.
The LNA 201 and the VGA 205 may operate under a control of the AGC 211, and the AGC 211 controls an operation of each of the LNA 201 and the VGA 205 by controlling a gain of each of the LNA 201 and the VGA 205. The LNA 201 amplifies a power of a signal received through an antenna by multiplying the signal received through the antenna by a preset gain value, and outputs the amplified signal to the mixer 203. The mixer 203 down converts the signal output from the LNA 201 by mixing the signal outputted from the LNA 201 with a preset frequency signal, and outputs the down converted signal to the VGA 205. The VGA 205 amplifies the down converted signal output from the mixer 203 by multiplying the down converted signal output from the mixer 203 by a preset gain value, and the amplified signal to the A/D 207. The A/D 207 generates an In phase & Quadrature phase (I/Q) signal by converting the signal outputted from the VGA 205, i.e., an analog signal to a digital signal, and outputs the I/Q signal to the MODEM 209. The MODEM 209 de-modulates the signal output from the A/D 207 using a preset de-modulation scheme, and outputs the de-modulated signal.
The signal output from the MODEM 209 is input to the AGC 211, and the AGC 211 determines a gain value of each of the LNA 201 and the VGA 205 included in the terminal using an average power of the signal output from the MODEM 209. An operation in which the AGC 211 determines the gain value used in each of the LNA 201 and the VGA 205 will be described below.
After detecting a receive power of a signal received during a previous preset time interval TWINDOW, the AGC 211 maps a total range for a signal output from the VGA 205 to a total available dynamic range of the A/D 207 by controlling a gain value of each of the LNA 201 and the VGA 205. That is, the AGC 211 minimizes a quantization noise and a performance decrease due to saturation by generating a control signal which controls the gain value of each of the LNA 201 and the VGA 205, and by transmitting the control signal to each of the LNA 201 and the VGA 205. However, if the structure of the related-art terminal, as described in FIG. 2, is used in a communication system using at least two beam widths, signal distortion and a quantization error may occur.
So, there is a need for controlling a gain without signal distortion and a quantization error in a communication system using at least two beam widths.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.